Jinko Solar’s 20% efficiency mc-Si solar cell is based on two major technologies, RIE texturing on DW wafer and PERC.
RIE texturing leads to very low surface reflectance, resulting in more incident light absorbed by silicon wafers. This will contribute significant gain on current. Moreover, since the size of pyramids formed by RIE texturing is in the scale of hundreds of nanometer, the Black Silicon solar cells can absorb the light with low incident angle, in others words better low intensity spectral response. DW mc-Si wafers pose advantages on low cost and low saw damage. But unfortunately traditional HF/HNO3 acid texturing cannot form good pyramids on DW mc-Si wafers. However, RIE texturing can form uniformly good texturing on DW mc-Si wafers. By utilizing the low sawed damage, the Black Silicon solar cells made on DW mc-Si wafers usually show 5mV gain on Voc.
PERC is well established technology in the industry. The gain in efficiency is mainly from reduced rear surface recombination and enhanced long wavelength spectral response. By combining RIE texturing on DW wafers and PERC, the average efficiency of mc-Si solar cell exceeds 20%.
It is also surprising to observe that the adding of improvement from RIE texturing on front side and improvement from PERC on rear side leads to additional gain, so-called 1+1>2.
Above is the process flow of Jinko Solar’s 20% efficiency mc-Si solar cells. The use of DW mc-Si greatly reduced the cost of silicon materials. DW technology has been widely used on mono-Si wafers, results in 6-7 US cent cost reduction per wafer. The application of DW technology on mc-Si wafers will help mc-Si wafers to regain cost advantage over mono-Si wafers. The replacement of slurry sawing by DW sawing will also reduce the use of slurry, making the wafer sawing process more clean and environmental friendly.
RIE technology is not new, but is not widely accepted in the past. The reason is that the efficiency gain of RIE technology is mainly from current (low reflectance leads to more light absorption) which will lose mostly during module assembly. Hence, the gain in module power is neglectable from RIE technology. However, in the case of DW mc-Si wafers, RIE is the sole technology can solve the texturing problems of DW mc-Si wafers and the gain of Voc due to low saw damage from DW mc-Si wafers can effectively improve module power. This makes both technologies cost effective.
Here are some of the advantages by Ealge PERC product series:
1, The combination of RIE technology and DW mc-Si wafers, leading to both low cost and high efficiency.
2, The innovative pre-clean and post-clean process on RIE texturing wafers. The pre-clean process makes the silicon wafer surface low damage and better for nano-scale pyramid formation. The post-clean process removes plasma damage during RIE texturing and modifies the pyramid morphology to help further surface passivation.
3, The thermal oxidation process to passivate RIE texturing formed nano-scale pyramids.
4, The combination of RIE and PERC leads to 1+1>2 effect.
1, Jinko Solar is the first one to mass produce 20% efficiency RIE+PERC DW mc-Si solar cells, with both advantages on low cost and high efficiency.
2, The Black Silicon solar cells and modules greatly improve aesthetics, and are welcomed by our high-end customers. Usually we will have 10-15% higher ASP for these products.
3, RIE+PERC products will improve low intensity spectral response and thus generate more electricity than standard products. This will bring more value to our customers and also reduce the final leverged cost of electricity of solar systems.
High efficiency mc silicon solar cells produced by Jinkosolar. A. Front side. B. Back side.
High power module made with high efficiency mc silicon solar cells. A. module with black back sheet. B. module with white back sheet.